Chains are employed as conveyor chains for operating scraper conveyors in underground coal mining. A scraper conveyor or scraper chain conveyor can have two rotating motor-driven conveyor chains with scrapers secured between the chains, connecting them. In appropriate applications such conveyor chains can also be arranged in a scraper chain conveyor as a center chain, in particular as a double center chain. During operation the scraper conveyor chains are drawn over a conveyor trough such that the excavated material, such as coal, is conveyed through the scraper and is carried away and transported.
The conveyor chains of such scraper conveyors were originally formed of uniform round links inserted into one and other. As more powerful drive units are used, there is a need for higher loading capacity chains employed as conveyor chains. To meet these demands larger diameter links, with a consequentially greater cross sectional area, are utilized in the prior art. However, the use of links with larger material diameter necessitates that the links, and therefore the chains, have a greater outer width.
While there are generally no disadvantages to this with chains used in horizontal applications, an increase of the material diameter the links in chains used vertical applications leads to an increase of the height of the scraper conveyor. Due to the frequently cramped spatial conditions in underground coal mining, especially when mining lodes of narrow thickness, it is desirable to keep the height of a scraper conveyor as low as possible. For this reason conveyor chains, also called flat chains, have been developed.
When vertical the shanks connecting the curvatures of flat chains have a diameter greater in the horizontal direction and smaller in the vertical direction compared to the cross sectional axes in the region of the curvatures. Consequently, the shanks of such links have a compressed, flattened cross section compared to the round cross section of the curvatures. Such conveyor chains serving as link chains are disclosed in DE 32 34 137 C2 or DE 197 24 586 C1.
In prior art flat chains, the primary consideration is not to reduce the cross sectional area of the flat chain links despite the flattening. Deviations of approximately 5 to 8% caused by the change of the cross sectional form of the shanks of the flat chain links are accepted as a necessity. In the prior art the aim was to minimize the reduction of the cross sectional are for the shanks compared to the curvatures, or to prevent any reduction. The problem is that any excessive reduction of the cross sectional area of the shanks would run counter to the expected increase of loading capacity of such a chain caused by the increase of the material diameter overall.
Nevertheless, against the described background there is the need for conveyor chains that have high tensile load capacity and a low structural height of their vertically oriented links. Put another way, there is a need for a conveyor chain in which the height of the vertically oriented links is lowered without loosing tensile load capacity. With increased tensile load capacity larger tonnages can be conveyed and/or conveying distances can be increased.
The present invention addresses the problem of further developing an above cited chain according to the species, in particular for use as a conveyor chain in underground coal mining, such that it meets the above listed aims.